The unfixable mystery problem
 

I have an 88 n/a auto supra from california, that has all the extra sensors and other goodies, with a faulty speed sensor. Other than that, the car runs fine except that if you floor it, the car will rev up to 4000k and then stop and not go any higher. If you push the pedal down 3/4 of the way, it will rev above 4000 up until redline. I have the car in at a mechanic that has knowledge of these kinds of cars. They've checked the fuel pressure, the distributor, they looked for some sort of rev limiter, they've looked for vacuum leaks, and nothing. I have no more ideas (nor does the mechanic) of what could be wrong on this car and it's really starting to frustrate me. If anyone has any clue as to what could be causing this, I would greatly appreciate your input. Thank you very much!

P.S. I have another car that is the exact same as this one from Canada that I'm using as a parts car. The mechanic suggested I get it towed there for random part swapping and I'm thinking I will have to resort to this but I'm hoping not.

I have a 87 turbo that is doing the same thing..... if any one know's what can cause this please let us know so we can get it fixed...

I have the same problem I just decided to swap out the engine and disasemble the old one but i couldent find anything I think it had to do something with comprasion and fuel cut off not sure tho

Luckily I do have a spare engine... however, that is a last resort. Perhaps I'll get a compression test done to see what it's doing. As for fuel cut, I don't think that's an issue as the mechanic said that when the engine is bogging at 4-5k, the fuel pressure is actually increasing. The TPS has also been ruled out... There may be a vacuum leak, but I'm unsure if it would cause that much of a problem. If anyone else has any ideas, I would gladly entertain them.

????
 

I had a similar problem and it was actually a misfiring at high rpm.(this is not what it felt or sounded like.) New valve cover gasket, plugs and wires solved the problem for me. Oh i changed original fuel filter (88 turbo). took me longer to do the filter than the gasket, plug and wires!

if it is a vac leek get some newspaper and light it on fire keep it away from the filter and run it around the vac lines and if you get a blow or suck of air cheak around that air for a leek

Just for an update, I guess the mechanic tested compression and said it was very strong. He's going to check the timing belt for missing teeth as he said that could be an issue. He also didn't think that a vacuum leak would cause this problem.

hmm, I know on my '88 supra I'm using as a donor motor for my '87 in much better shape that it had some old hoses and lines on it that were all split and it completely sucked the power right out of it.

That is a good suggestion, however, that is not the case with this problem. The car will run fine with lots of power up until 4k. After that, the car simply feels like it is not getting more power. If you depress the accelerator to about 3/4, you can rev it to redline. If you put it right to the floor, it will stop revving at 4k.

Sounds like their is some kind of limiter on your electronics end. Have you checked into the fuelcut? I know HKS makes a fuel cut defender (FCD), you could look into this. It might solve your problem.